xcodebuild -create-framework error: unable to read the file

Here are step by step instructions, I think you might be missing step 2:

1) Set Build Library for Distribution in the build settings for the target framework to YES

2) Again in the build settings, set Skip Install to NO otherwise the framework won't show up in the Archive output folder.

3) Archive from the Xcode Product menu after selecting your Generic iOS Device the output will appear in the Organizer. Control-Click on the Archive. Select Show in Finder Drag that to the terminal to get the path to the archive and append the path (yellow part is the dragged path, gray is navigated in subfolders). In this case it looks like this, I used the ~ to avoid showing entire path.

~/Library/Developer/Xcode/Archives/2019-06-22/Output\ 6-22-19,\ 11.50\ AM.xcarchive/Products/Library/Frameworks/MyFramework.framework

4) Then create the XCFramework by inserting the command in front of the above path:

xcodebuild -create-xcframework -output Output.xcframework -framework ~/Library/Developer/Xcode/Archives/2019-06-22/Output\ 6-22-19,\ 11.50\ AM.xcarchive/Products/Library/Frameworks/MyFramework.framework 

5) You then should see the output:

xcframework successfully written out to: ~/Project/Output.xcframework

I expect that someday soon Xcode will add a the ability to directly create the XCFramework without the command line.

You have to do a two step process via the command line.

1. xcodebuild archive

This will archive the framework and stick it likely in the build directory of your project.

2. xcodebuild -create-xcframework -output FrameworkName.xcframework -framework build/Release-iphoneos/ArchivedFramework.framework

This should successfully generate the XCFramework.

You typed the command wrong:

xcodebuild -create-xcframework -framework /path/sample.xarchive -output sample.xcframework

In my case it was failing for iPhone as arm64 architecture was added in the Excluded Architecture in Build Settings